VEHICLE STABILITY CONTROL SYSTEM, Diagnostic DTC:C1426

DTC Code DTC Name
C1426 Stop Light Switch OFF Stuck Malfunction

DESCRIPTION

The skid control ECU (brake actuator assembly) inputs the stop light signal and brake operation condition. When the brake pedal is depressed and the stop light switch signal is not input, C1426 is output.

DTC No. Detection Item DTC Detection Condition Trouble Area
C1426 Stop Light Switch OFF Stuck Malfunction When voltage at terminal +BS is 9.5 V or higher, vehicle is driven and brake pedal is operated, stop light switch signal is not input.

  • Wire harness or connector

  • STOP fuse

  • Stop light switch assembly

  • Skid Control ECU (Brake actuator assembly)

WIRING DIAGRAM

Refer to DTC C1380.

Click here

CAUTION / NOTICE / HINT

Note


  • When replacing the skid control ECU (brake actuator assembly), perform zero point calibration and store system information.

    Click here

  • Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE


  1. CHECK BRAKE PEDAL AND STOP LIGHT SWITCH INSTALLATION


    1. Check the brake pedal height installation.

      Click here

    2. Check the stop light switch assembly installation.

      Click here

      OK
      The brake pedal height and stop light switch assembly installation are normal.

      Tech Tips

      If the on/off status of the stop light switch assembly and pressure increase information from the master cylinder pressure sensor do not match due to an improperly installed brake pedal or stop light switch assembly, this DTC may be stored. Therefore, be sure to check the installation condition of the pedal and switch before inspecting the input signals and other related parts.

      Result
      Proceed to
      OK
      NG

    NG

    ADJUST BRAKE PEDAL OR STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  2. CHECK STOP LIGHT OPERATION


    1. Check that all stop lights come on when the brake pedal is depressed, and go off when the brake pedal is released.

      OK
      Condition Illumination Condition
      Brake pedal depressed. On
      Brake pedal released. Off
      Result
      Proceed to
      OK
      NG

    NG

    INSPECT STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  3. READ VALUE USING GTS (STOP LIGHT SWITCH ASSEMBLY)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Select the Data List using the GTS.

      Click here


      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Stop Light SW Stop light switch ON or OFF

      ON: Brake pedal depressed

      OFF: Brake pedal released

      		 -

      Chassis > ABS/VSC/TRC > Data List
      Tester Display
      Stop Light SW

    4. Check that the stop light switch display observed on the GTS changes according to brake pedal operation.

      OK
      The GTS displays ON or OFF according to brake pedal operation.
      Result
      Proceed to
      OK
      NG

    NG

    CHECK HARNESS AND CONNECTOR (STP TERMINAL) Click here

    OK

  4. RECONFIRM DTC


    1. Turn the ignition switch off.

    2. Clear the DTCs.

      Click here


      Chassis > ABS/VSC/TRC > Clear DTCs

    3. Start the engine.

    4. Depress the brake pedal several times to test the stop light circuit.

    5. Check if the same DTC is recorded.

      Click here


      Chassis > ABS/VSC/TRC > Trouble Codes
      Result
      Result Proceed to
      DTC C1426 is not output. A
      DTC C1426 is output. B

      Tech Tips

      If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step.

      Click here


    A

    USE SIMULATION METHOD TO CHECK Click here

    B

    REPLACE BRAKE ACTUATOR ASSEMBLY Click here

  5. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Check the stop light switch assembly.

      Click here

      OK
      The stop light switch assembly is normal.
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  6. CHECK HARNESS AND CONNECTOR (STP TERMINAL)


    1. Turn the ignition switch off.

    2. B0024ICC64
      *a

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly))

      Make sure that there is no looseness at the locking part and the connecting part of the connector.

    3. Disconnect the A4 skid control ECU (brake actuator assembly) connector.

    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A4-35 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 8 to 14 V
      Stop light switch assembly off (Brake pedal released) Below 1.5 V
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

    OK

  7. RECONFIRM DTC


    1. Reconnect the A4 skid control ECU (brake actuator assembly) connector.

    2. Clear the DTCs.

      Click here


      Chassis > ABS/VSC/TRC > Clear DTCs

    3. Turn the ignition switch off.

    4. Start the engine.

    5. Depress the brake pedal several times to test the stop light circuit.

    6. Check if the same DTC is recorded.

      Click here


      Chassis > ABS/VSC/TRC > Trouble Codes
      Result
      Result Proceed to
      DTC C1426 is not output. A
      DTC C1426 is output. B

    A

    USE SIMULATION METHOD TO CHECK Click here

    B

    INSPECT LIGHTING SYSTEM (STOP LIGHT CIRCUIT) Click here

  8. CHECK HARNESS AND CONNECTOR (STP TERMINAL)


    1. Turn the ignition switch off.

    2. B0024ICC64
      *a

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly))

      Make sure that there is no looseness at the locking part and the connecting part of the connector.

    3. Disconnect the A4 skid control ECU (brake actuator assembly) connector.

    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A4-35 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 8 to 14 V
      Stop light switch assembly off (Brake pedal released) Below 1.5 V
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE BRAKE ACTUATOR ASSEMBLY Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)